This invention relates to tubular food casings, especially sausage casings, comprising a smoke component that will transfer smoke color and/or flavor to the surface of food products contained within the casing.
Food casings have been made from a variety of materials that are in tubular form or can be formed into tubes. Examples of such materials are natural gut, synthetic plastics, cellulose films, and fabrics. The materials may be reinforced with fibrous materials or may be unreinforced. The material primarily used for the manufacture of food casings is cellulose that is either precipitated from solution or regenerated from a solution of a cellulose derivative. Cellulose and derivatized cellulose solutions may collectively be referred to herein as "viscose". The term "viscose" as used herein is intended to mean a solution of either non-derivatized or derivatized cellulose in a suitable solvent, e.g. xanthated viscose in alkali, cellulose in amine oxide solution, cellulose amino methanate in alkali or cellulose in cupraammonium solution. Formation of cellulose by precipitation or regeneration from viscose is collectively referred to as regeneration, i.e. re-formation of solid cellulose from solution. Food casings made from film materials by precipitation of cellulose from solution or by regeneration of cellulose from a solution of a cellulose derivative, e.g. xanthate viscose, have been found to have many very good qualities. In particular cellulose is very hydroscopic while being completely water insoluble. Cellulose films have good smoke permeability. Cellulose films have good dimensional stability. Cellulose films have good strength and cellulose films can be made from readily available raw materials. Formation of cellulose film food casings from viscose has, however, been considered "touchy" since even slight changes in processing parameters can adversely affect film properties.
Smoke has long been applied to food products for purposes of flavor and preservation. Among such food products, sausages of various kinds have often been smoked. Traditionally when natural food casings, i.e. gut casings, were used, food product was stuffed into the casing and the resulting stuffed product, especially sausages, were smoked in a smoke house where the product was exposed to smoke vapors to impart smoke flavor, aroma and color to the contained food product. This process has continued to the present where products contained in food casing made of various natural and synthetic materials are exposed to smoke vapors. Such materials include collagen, synthetic plastics such as nylon and regenerated cellulose, i.e. cellulose regenerated from a solution of a cellulose derivative or cellulose precipitated from a solution of cellulose in a suitable solvent, e.g. tertiary amine oxide cellulose solution or cupraammonium cellulose solution. Any of such materials may be reinforced, e.g. with fibers blended into the material or in the form of a woven or felted web or mat impregnated with the material.
Such a smoke process for contained food, e.g. meat, product is costly and time consuming. In addition, all food casings are not suitable for such a process since smoke penetration through the casing to the food product may be poor or even non-existent. In addition, non-uniform product may result, e.g. due to the nature of the casing product. Such casing product may, for example, have areas of reduced smoke penetration, such as the seam area in fiber reinforced casing where the casing is thicker or printed casing where the smoke may not easily penetrate printed areas. In addition the amount of smoke application may depend upon the position of the stuffed food product in a smoke house where variations in smoke density are likely to occur.
Various attempts have been made to overcome the defects previously described. For example attempts have been made to directly incorporate smoke flavorants into sausage meat product. This in itself has several disadvantages. In particular, such incorporation does not simulate natural smoke flavor where smoke components are concentrated in the food product, e.g. meat or cheese, near the surface rather than being uniformly distributed through the food product. Concentration near the surface not only gives rise to a pleasant variation in flavor through the product but also results in a pleasing smoke color at the surface of the product. Any attempt to add smoke materials to food product sufficient to obtain such a smoke color therefore requires much more smoke than is necessary to obtain a similar depth of color by exposure to smoke vapor. This excess addition may result in an undesirable oversmoked flavor. Numerous attempts have been made to overcome this problem by adding dyes to food products, such as meat, which is viewed as undesirable and in some cases actually prohibited by law. Attempts have also been made to fractionate colorants from smoke without obtaining flavor components, which is time consuming, relatively more expensive and usually does not result in colorants having the same hue as unfractionated smokes.
It has been long known that smoke products could be applied to food casings to transfer smoke color, smoke flavor or both to products contained in the casing. Reference may for example be had to British Patent Specification 589,274, having a British filing date of Mar. 21, 1945. That British patent publication discloses applying smoky fractions of wood distillates into the film composition of a casing for sausage or other food product or onto the surface of such a casing to give a smoky odor and flavor to contained food product. The disclosure of the British Patent Application clearly contemplates that distillates are obtained by destructive distillation of wood followed by using fractions of such distillates for application into or on the food casing.
Such a process has deficiencies in that distillates are a complex mixture of substances some of which are tar-like materials, others of which are water insoluble liquids of various viscosities and other of which are water soluble or are at least water dispersible. It is therefore difficult to uniformly apply all distillate fractions to the surface of a food casing.
Attempts have also been made to use various modified and unmodified liquid smokes for application to meat products and food casings to obtain flavor or color. Liquid smokes are generally formed by passing smoke vapor through an aqueous system which absorbs components of the smoke. Numerous patents have been granted with respect to liquid smokes and their use. A few representatives of such liquid smoke patents are U.S. Pat. Nos. 4,104,408; 4,442,868; 4,446,167; 4,504,500; 4,505,939; 4,604,309; 4,657,765; 4,717,576; 4,905,587; and 4,933,217. There are problems associated with application of liquid smokes to food product which in many ways are similar to application of smoke distillates. For example, incorporation of liquid smoke into meat product gives rise to the same considerations as incorporation of smoke distillates, i.e. incorporation gives a uniform distribution which does not replicate surface application resulting from directly smoking with smoke vapor with respect to either flavor or color. Additionally, due to effects of gravity and tendency for many liquid smoke compositions to separate, it is difficult to uniformly apply liquid smokes to the surface of either food product or food casings intended to transfer color or flavor to contained food product. In addition, transfer from food casings coated with a liquid smoke composition is not as good as desired.
Yet further, the use of liquid smokes on the surface of food casings results in food casings that are not uniformly smoke coated, sticky, difficult to shirr, that pollute and gum up rollers and other casing handling apparatus, that have a tendency to be self adherent thus causing inconsistent deshirring or unrolling on a food packaging machine, that exude an unpleasant smoke odor and that do not cleanly peel from contained food product after the food product is processed. Casings containing sufficient moisture to provide the flexibility needed for stuffing have an additional problem in that the surface smoke often results in unsightly and messy food casing packages containing residual smoke liquid that can and does easily leak or drip from the package when the package is opened to obtain the food casing for placement onto food stuffing equipment.